Ultrasensitive Bi2O2Se phototransistors are demonstrated by utilizing a unique method to transfer CVD‐grown Bi2O2Se from mica onto silicon substrates. Compared with devices on mica, photodetectors on silicon maintain high photoresponsivity, high photoconductive gain, fast response rate, and at the same time, the dark current is much lowered, which yields ultrahigh on/off ratio and specific detectivity. Abstract 2D materials are considered as intriguing building blocks for next‐generation optoelectronic devices. However, their photoresponse performance still needs to be improved for practical applications. Here, ultrasensitive 2D phototransistors are reported employing chemical vapor deposition (CVD)‐grown 2D Bi2O2Se transferred onto silicon substrates with a noncorrosive transfer method. The as‐transferred Bi2O2Se preserves high quality in contrast to the serious quality degradation in hydrofluoric‐acid‐assisted transfer. The phototransistors show a responsivity of 3.5 × 104 A W−1, a photoconductive gain of more than 104, and a time response in the order of sub‐millisecond. With back gating of the silicon substrate, the dark current can be reduced to several pA. This yields an ultrahigh sensitivity with a specific detectivity of 9.0 × 1013 Jones, which is one of the highest values among 2D material photodetectors and two orders of magnitude higher than that of other CVD‐grown 2D materials. The high performance of the phototransistor shown here together with the developed unique transfer technique are promising for the development of novel 2D‐material‐based optoelectronic applications as well as integrating with state‐of‐the‐art silicon photonic and electronic technologies.
Published in: "Advanced Materials".